CANKERWORMS SNODGRASS 



323 



Fig. 7. — Mature spring- cankerworm in resting 

 attitude, showing lack of abdominal prolegs ex- 

 cept those on sixth and tenth abdominal seg- 

 ments (X 21^) 



abdominal segment there is a pair of small tubercles. There are 

 always only two pairs of abdominal prolegs as described above. 



In observing cankerworms on an apple tree or in collecting speci- 

 mens, however, it will most likely be noticed that they are not all 

 alike. Some have the characters of those just described, while others 

 are marked often by several distinct lines along the sides of the 

 body, but are definitely sepa- 

 rable as different by the 

 presence of an extra though 

 a small pair of prolegs on 

 the fifth segment of the ab- 

 domen, which is the segment 

 next in front of that bearing 

 the first pair of fully- 

 developed prolegs. Cater- 

 pillars of this sort (fig. 8) 

 belong to a distinct species 

 known as the fall canker- 

 worm {Alsopltila pometaria) because the moths that produce them 

 appear mostly in late fall and deposit their eggs on the trees at this 

 season. The eggs of both species hatch at the same time in the 

 spring. 



The fall cankerworms are in general of a greener color than the 

 spring cankerworms, but different individuals vary from light green 

 to dark olive brown. Most of them have three distinct pale stripes 



along each side of the body, and an 

 occasional one has a large blackish spot 

 on each side of each segment between 

 the lower two lines. 



For a month the caterpillars of the 

 two species of cankerworms feed to- 

 gether in the trees, where to the casual 

 observer they all look alike, both kinds 

 having the same general appearance and 

 size and the same looping gait. They 

 Fi(j. 8.— Mature fall canker\vorm, botli, also, wlieu at rcst have the quecr 



showing presence of mdimentary a \ ■, e • , • ij?/^! 



prolegs on fifth abdominal segment ^'^^^^^ ^^ graSpiUg a twig Or leaf firmly 



with the abdominal feet and holding 

 the body stiffly in the air, projected at an angle from the sup- 

 port. They pose motionless in this attitude indefinitely and appear 

 to be impersonating a dead twig in order to fool their enemies. 

 They may sometimes elude the searching eye of an entomologist 

 or of a bird, but still the habit can not be of any great benefit 

 to the cankerworm species, since a bird could always find plenty of 

 active individuals feeding unconcerned. The trait, however, is one 



